In general, since a semiconductor manufacturing process for manufacturing a semiconductor device requires a high degree of precision, a high degree of cleanliness and a special manufacturing technique are required.
Due to the above-mentioned reason, a product having high reliability and a high degree of completion may be manufactured in a state in which the semiconductor device is completely prevented from contacting foreign substances contained in the air, i.e., a vacuum state.
Meanwhile, a vacuum pump suctioning the air and other gases in a process chamber is installed outside the process chamber to maintain the vacuum state in the process chamber for manufacturing the semiconductor device.
Also, a gate valve is installed between the process chamber and the vacuum pump. The gate valve may be opened when the vacuum pump discharges the air and other gasses in the process chamber and closed when the vacuum state in the process chamber is maintained to always maintain the inside of the process chamber in the clean vacuum state.
In a rectangular gate valve including an air cylinder maintaining vacuum by using O-rings to ascend/descend a shaft and a main body including a rectangular disk and a rectangular passage thereabove, the mount type rectangular gate valve disclosed in the following patent document 1 (Korean Patent Publication No. 2003-0050409) of the above-mentioned gate valves includes a rectangular opening/closing disk hinge-coupled to the cylinder shaft and including four mounting rolls respectively provided on edges of the rectangle, rolling rolls configured to roll left and right side surfaces, and a rectangular O-ring sealing edges of a front surface of the disk, four mounting balls having an upward angle corresponding to the mounting roll and defined in an inner rear surface of the main body of the rectangular gate valve, and three ball plungers each of which protruding from an inner front surface of the main body and biased to left and right sides, to always apply force in a direction in which the rectangular opening/closing disk is away from a front surface of the main body, thereby ascending/descending the rectangular opening/closing disk by ascending/descending movement of the shaft and closely attaching the rectangular opening/closing disk including the O-ring to a passage of the front surface as the mounting roll mounts the mounting ball to completely seal. Thus, a sealing effect between the disk and the passage may be high and the disk may be easily manufactured.
However, when a mechanical defect is generated in the air cylinder, the mount type rectangular gate valve disclosed in the patent document 1 may not perform a typical function of closing a passage because a separate alternative opening/closing unit is not provided. Thus, management and repair of the mechanical defect may not be instantly performed.
Also, since a component for guiding vertical movement of the rectangular opening/closing disk is not provided in the air cylinder, the shaft connected to the air cylinder may not exactly move upward and downward due to difference of a pneumatic pressure in the air cylinder. Thus, vertical and horizontal movement of the rectangular opening/closing disk may not be smoothly performed.